The present invention relates generally to control methods and systems for robotic manipulators. More particularly, the invention relates to a system for generating robotic manipulator trajectories.
Performing Cartesian control of robotic manipulators involves interpolating a Cartesian trajectory (position, velocity and acceleration) and converting this Cartesian trajectory into an equivalent joint space state. The position conversion is performed using the inverse kinematics mapping of the manipulator. However, the conventional method of computing the joint velocities is by taking the difference between consecutive joint positions and dividing it by the interpolation period. This approach inherently jeopardizes path accuracy at low servo update rates and high accelerations. Furthermore, it can produce non-smooth trajectories.
Therefore, it is an object of the present invention to generate robotic system trajectories with improved accuracy.
Additionally, it is an object of the present invention to generate smooth trajectories for a robotic system.
The present invention provides a trajectory generation system to operate a robot in response to a motion command. The robot is a multi-jointed manipulator with an end-effector that traverses a trajectory. A Cartesian trajectory generator converts the motion command into a requested Cartesian positions vector and a requested Cartesian velocities vector. A Jacobian matrix of the manipulator defines the relationship between the manipulator joint velocities vector and the manipulator Cartesian velocities vector. A requested joint velocities vector is computed from the requested Cartesian velocities vector by means of the inverse of the Jacobian matrix. A requested joint positions vector is computed from the requested Cartesian velocities vector by means of inverse kinematics. The requested joint velocities vector and requested joint positions vector define a planned state vector for the manipulator.
For a more complete understanding of the invention, its objectives and advantages, refer to the following specification and to the accompanying drawings.